1. Technical Field
The present disclosure relates to a vehicle external environment recognition device that identifies a specific object to which an object existing within a detection area corresponds.
2. Related Art
There are conventionally known a technique, such as collision avoidance control, which detects specific objects including another vehicle located ahead of a vehicle and avoids a collision with a leading vehicle, and a technique, such as a cruise control, which controls so as to maintain an inter-vehicle distance with a leading vehicle at a safe distance (for instance, see Japanese Patent No. 3,349,060 and Japanese Unexamined Patent Application Publication (JP-A) No. 2010-224925).
Especially in cold weather and/or high altitude locations, a lump of steam may be floating on the road surface or white exhaust gas may be discharged from an exhaust pipe of the leading vehicle, and they may remain still without spreading immediately. When the above conventional control techniques are used, the floating matters, such as steam and exhaust gas, are misjudged to be specific objects, such as a vehicle and a pedestrian, whereby a stopping control or a slowdown control may be actuated to avoid the specific objects.
For this reason, for example, JP-A No. 2009-110168 discloses a technique that calculates an average of distances of parts of a detected object and calculates variations (distributions) in the distances of the object parts with respect to the average to determine that the detected object is the floating matters, such as steam and exhaust gas, which the vehicle will be safe to collide if the variations exceed a threshold. Moreover, for example, JP-A No. 2012-243049 discloses a technique that groups subject parts located within a detection area as one object based on relative distances of the subject parts, and determine whether the object is white floating matters based on any one or more of characteristic amounts, such as an average value, a variance, a skewness, and a kurtosis of luminance, obtained from a histogram of luminance of the object.
However, for example, in a windless condition, the floating matters such as steam and exhaust gas may remain still (stay) on the road surface. In such a case, since the variation in distance of parts of the floating matters becomes small, it is difficult to distinguish between the floating matters and the specific objects by the technique disclosed in JP-A No. 2009-110168. Further, because the distributions in distance of the floating matters may have a wide variety of patterns, the distributions in distance which are typical characteristics of the floating matters cannot be recognized exactly only based on the variations, resulting in a comparatively low detection accuracy of the floating matters.
Further, for example, if colored lights of traffic lights and/or streetlights reflect on the floating matters to glow the floating matters in the illuminated colors, the detection accuracy of the floating matters cannot be improved only by the technique of determining the color of white as disclosed in JP-A No. 2012-243049.